Method and arrangement for integrity-testing of a tube-set for use in a cycler for peritoneal dialysis

ABSTRACT

Methods and apparatus are disclosed for testing the integrity of a tube set used in a cycler for peritoneal dialysis comprising a closable housing for at least a portion of the tube set and an air pump for subjecting the housing to an underpressure or an overpressure, and clamps for clamping portions of the tube set passing into the housing. The method includes subjecting the housing to a first overpressure with the clamps closed whereby a first pressure leakage is observed, subjecting the housing to a second overpressure with the clamps open whereby a second pressure leakage is observed, and comparing the first and second pressure leakages so that action can be taken based upon that comparison.

TECHNICAL FIELD

The present invention relates to a method and an arrangement in amachine for carrying out peritoneal dialysis. More specifically, theinvention relates to a method and arrangement for integrity-testing of atube-set for use in a cycler for peritoneal dialysis

PRIOR ART

Peritoneal dialysis, hereinafter abbreviated to PD, can be carried outmore or less manually in a so-called CAPD treatment, where CAPD standsfor “continues ambulatory peritoneal dialysis” or with help of a machinein a so-called APD treatment, where APD stands for “automated peritonealdialysis”.

Liquid for PD is delivered in a sterile form in supply bags which areconnected to the patient via a tubeset and a catheter which terminatesin the abdominal cavity of the patient. When used in connection withAPD, the tube-set comprises a heat bag to which the PD liquid isinitially conveyed in order to be heated to body temperature. The liquidhas a composition which is suitable for PD. Normally, it includesglucose as an osmotic agent.

A machine which is commonly termed a cycler is used during APD forregulating the supply and removal of liquid to and from the peritonealcavity in the patient's abdominal cavity via the catheter.

Such a cycler is described in WO 95/20985 and comprises a casing whichencases said heat bag as well as a discharge bag. An underpressure andan overpressure respectively can be created in the casing via an airpump to thereby drive the liquid into and out of the bags. Inlets andoutlets to the bags pass through respective bushings in the wall of thecasing.

A problem which arises in connection with a cycler of the type which isdescribed in WO 95/20985 is the following. If there is a hole in thatportion of the tube-set which is located within the casing, i.e. a leakin the bag, the connection between tube and bag or the tube from the bagto or in the bushing, there is a risk that PD liquid can leak out of thebag and collect at the base of the casing.

Such a hole may arise due to faulty material, because the weldingbetween the bag and the tube is unsatisfactory or due to the effect of asharp object in connection with the use or other careless handling ofthe bag.

U.S. Pat. No. 5,350,357 discloses a cycler comprising leak testing ofthe disposable set. Such leak testing is performed as a one stepprocedure at low or high pressure. This leak testing procedure requiresaccess to the interior of the disposable set.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to provide a methodand an arrangement which permits checking if there is a risk of leakage.

In accordance with the invention, the portion of the tube-set which islocated within the casing is subjected to an integrity-test before themachine is allowed to commence the dialysis treatment.

The machine is started and performs its normal function test in whichall of the essential functions and safety systems of the machine aretested. During this function test, the machine is attired with thesterile tube-set. Supply bags are connected to the inlet tubes. Thepatient connection is placed in a special priming position. When thefunction test has been performed, the machine adopts a stand-bycondition. When the patient has attached the tube-set, the patientpresses a pre-rinse button. Before the actual pre-rinse or priming ofthe tube-set, an integrity-test according to the invention is performed.

By means of an air pump, an overpressure of a predetermined amount iscreated in the casing outside the tube-set, whereby the outlets from thetube-set are open. When the predetermined air pressure has been reached,the pump is stopped and the clamp arrangements are closed. The air canthus exit the casing via a possible leakage which is always present insuch a construction, for example between the cover and base of thecasing or via the bushings. A “normal” leakage implies that the pressureslowly reduces. The pressure sequence is recorded using a pressure meterfor a predetermined interval of time.

Thereafter, the pressure is once more increased in the casing to saidpredetermined pressure and the outlets via the tube-set are opened bymeans of clamps. The pressure sequence is once more recorded using thepressure meter for a predetermined interval of time.

If the pressure sequences are substantially identical for the first twotests, it is an indication that the tube-set has passed theintegrity-test. The tube-set is thereafter filled with liquid in aso-called priming stage.

If, on the other hand, the second pressure sequence leads to a morerapid reduction of the pressure than the first pressure sequence, it isan indication that there is a fault present. Thus, the machine can emitan alarm signal. Furthermore, the machine can be placed in a conditionwhich renders impossible continued use until a new tube-set is mountedand a new integrity-test has been executed.

Alternatively, the integrity-test can be performed with underpressure inthe casing or underpressure and overpressure in combination. Otheralternatives will be apparent from the following description.

According to the invention, the difference in final pressure is notallowed to be greater than the predetermined pressure differential valuefor the machine to be able to recognise that the integrity-test has beenexecuted in a satisfactory manner. Other methods of calculation can alsobe used.

The integrity-test can be combined with devices for sensing whetherliquid has leaked onto the base of the casing.

Thus, it is apparent that the invention makes possible a leak testwithout intervening into the interior of the tube-set, which issterilised before use and should be kept sterile. The inventiondiscriminates between a “normal” leakage and a leakage through a hole,which cannot be tolerated.

The invention will be described in greater detail below with referenceto an embodiment of the invention shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side-view of a tube-set intended for peritoneal dialysis andon which the present invention can be applied.

FIG. 2 is a perspective view of a cycler of a known type and equippedwith the tube-set according to FIG. 1 and on which the present inventionis intended to be applied.

FIG. 3 is a side-view of a portion of the cycler according to FIG. 2provided with the arrangement according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is intended to be used together with a cycler which isshown in FIG. 2 and a tube-set which is shown in FIG. 1, which drawingsare taken from WO 95/20985.

The tube-set 1 is provided with a plurality of inlet tubes 2, 3, 4, 5, 6provided with connectors 7, 8, 9, 10, 11 for connection to supply bags12 of dialysis-solution, whereof only one is shown with dashed lines inFIG. 1. The number of tubes 2-6 is of course dependent on theapplication and is normally either five or ten. Each tube is providedwith a tube clamp 13, 14, 15, 16, 17 which, in the shown embodiment, ismanually operable.

The tubes 2-6 lead to a manifold coupling 18 and the flows combine intoa common first tube 19 which leads to an F-coupling 21. The tube 19 hasa tube clamp 20. A second tube 22 runs from the F-coupling to a heat bag23. The tube 22 is provided with a tube clamp 24. A third tube 25 runsfrom the F-coupling via a Y-coupling 26 to a connection 27 intended tobe connected to a catheter of the patient. A fourth tube 28 runs fromthe Y-coupling 26 to a second F-coupling 29. A fifth tube 30 runs fromthe F-coupling 29 to a discharge bag 31. In addition, a sixth tube 32provided with a tube clamp 33 runs from the F-coupling 29 to a connector34. The connector 34 is intended to be connected to a drain or a largecontainer (which can be a number of used supply bags).

The first tube 19, the third tube 25, the fourth tube 28 and the sixthtube 32 are provided with electromagnetically controlled clamparrangements 35, 36, 37 and 38 which are actuated electrically. The heatbag 23 and the discharge bag 31 are located in a pressure chamber as ismore clearly apparent from FIG. 2.

The tube-set 1 shown in FIG. 1 is intended to be used in a cycler 40which is shown in FIG. 2. The tube-set is only partially shown in FIG.2. The electromagnetically controlled clamp arrangements are arrangedpair-wise in clamp holders so that the clamp arrangements 35 and 36 arelocated in a first clamp holder 41 and the clamp arrangements 37 and 38are located in a second clamp holder 42.

It is apparent from FIG. 2 that the tube 22 is provided with a bushing43 and the tube 30 is provided with a bushing 44. The heat bag 23 andthe discharge bag 31 are located in a casing 45 which consists of alower portion or a base 46 and an upper portion or a cover 47, whichcover is affixed to the base via a hinge 48. A locking device 49 holdsthe cover 47 and the base 46 together so that the seal 50 there betweenis compressed and a substantially airtight joint is attained between thecover and the base. The bushings 43 and 44 fit into recesses in thecover and/or the base.

The cycler 40 comprises a display and control unit 51 positioned on thefront of the machine. Furthermore, there is an air pump 52 which, via atube 53, communicates with a connection 54 on the side of the casing.The connection 54 leads to the interior of the casing.

As is shown in FIG. 3, the base of the casing is provided at its centrewith a vertical rod 56 which rests on a load cell 57. The rod isinserted into a sleeve 58 arranged on the load cell such that the casingcannot lean in any direction. The casing 45 with contents can thus beweighed by the load cell 57.

The normal operation of this cycler is described in Wo 95/20985.Briefly, the air pump 52 is used to create underpressure andoverpressure in the casing 45.

A cycle commences with the heat bag containing PD liquid which has beenheated to body temperature.

The catheter of the patient is connected to the connector 27 and adrainage phase commences by opening the clamp arrangement 37 at the sametime that an underpressure prevails in the casing 45 where the drainagebag 31 is located. The bag 31 is thus filled with used PD solution fromthe patient which is monitored by the load cell.

When the drainage phase has taken place, the clamp arrangement 37 isclosed and the clamp arrangement 36 is opened and connects the heat bagto the patient. At the same time, the pump 52 is operated so that anoverpressure prevails in the casing 45. The contents of the heat bag arenow transferred to the patient during monitoring of the load cell.

When a suitable quantity has been transferred, the clamp arrangement 36is closed and the clamp arrangement 38 is opened. The pump 52 stillcreates an overpressure in the casing 45 so that, during monitoring viathe load cell, the drainage bag is emptied into a vessel connected tothe connector 34 (or directly to the drain).

Finally, the clamp arrangement 38 is closed and the clamp arrangement 35is opened at the same time that an underpressure is created by the pumpin the casing. New PD solution is supplied to the heat bag 23 fromsupply bags 12 connected to the connectors 7-11 during monitoring of theload cell. The new PD solution is heated to body temperature and thecycler is ready for a new cycle.

Reference is made to WO 95/20985 for a more detailed description of thesequence. WO 95/20985 is incorporated herein by reference.

If the tube-set has a leak in that portion which is within the casing,problems arise. If the leakage is great, which can be the case whenthere is faulty welding, the entire casing can be more or less filledwith PD solution. There is a risk that the solution in the casing willthereafter be fed to the patient. In other cases, there is a risk thatair will be fed to the patient instead of PD solution. It is obviousthat such conditions must be avoided.

If there are small holes, there is always the risk that bacteria canenter through the holes and cause infection. Such contamination shouldalso be avoided, for which reason it is just as important to be able todetect small holes.

It is possible to provide the cycler with mechanical or electricalsensors which sense if liquid is present in the lower portion of thebase 46. However, such liquid sensors require maintenance and canthemselves result in faulty operation.

By arranging the connection 54 of the pump in the lowest portion of thecasing, any liquid in the casing will be drawn to the pump during theunderpressure portion of the cycler's function. Such liquid in the pumpcan be electronically sensed and used to actuate an alarm signal.

These mechanical arrangements are, however, not able to take care of thesituation in which air is fed into the conduit to the patient. Possibly,this can be detected by the load cell registering a too small quantityof liquid fed to the patient.

In accordance with the present invention, another method is howeverprovided to remove the above-mentioned problem. The tube-set issubjected to an integrity-test before it is filled with liquid for thefirst time.

The tube-set is mounted to the cycler as has been described above and adesired number of supply bags 12 are connected to the connections 7-11and corresponding clamps 13-17 are opened. It is further ensured thatthe tube clamps 20, 24, 33 are open and that the clamp arrangements35-38 are closed. Thereafter, the button 55 is pressed for pre-rinsingor priming. Initially, however, an integrity-test is performed accordingto the invention. If the integrity-test is carried out faultlessly, themachine continues with priming and pre-rinsing of the tube-set asnormal. Since the integrity-test takes only a short time, the patientwill not normally notice that an integrity-test is taking place.

During the integrity-test, the pump 52 is activated at the same timethat the clamp arrangements 36 and 37 are opened and an overpressure isattained in the casing 45. The overpressure can for example be 40 mm Hg.Finally, the clamp arrangements 36 and 37 are closed and the pump isstopped, whereupon the pressure in the casing will slowly start to dropdue to the fact that the air exits through the seal between the coverand base as well as via the bushings. This first “normal” pressuresequence is monitored by a pressure meter 59 connected to the interiorof the casing 45. After a predetermined interval of time, for example 10seconds, the final pressure is read and the pressure drop is read asΔP₁.

The pump is reactivated to increase the pressure to the same pressure asbefore, i.e. for example 40 mm Hg. When the pump stops, the clamparrangements 36 and 37 are opened and the pressure slowly drops again inthe same manner as during the first pressure sequence. If a hole ispresent in the portion of the tube-set which is located in the casing,air will also pass through this hole to either the heat bag or thedischarge bag and thereafter out to the atmosphere via the open tube 19or the tube 32. After the predetermined interval of time, the pressurereduction is read as ΔP₂.

If this second pressure sequence is the same as the first pressuresequence, it is an indication that the tube-set does not have a leak. Ifthe pressure in the second pressure sequence drops more quickly thanduring the first pressure sequence, it is an indication that there is aleak since, during the second pressure sequence, a quicker pressure dropoccurs because of leakage which is released via the open connection 27.

If the difference between ΔP₂ and ΔP₁ is less than a predetermined valueΔP, for example less than 2 mm Hg, it is regarded that the tube-set haspassed the integrity-test. ΔP is selected such that normal variations inthe pressure drop do not activate the integrity-test. In addition, otherstipulations can be made separately or in combination, for example thatΔP₂ may not be more than 50% greater than ΔP₁. The calculations areperformed in a control unit 60 in the form of a microprocessor.

Our experiments show that, using this method, we are able to detectholes having a diameter less than about 0.3-0.4 mm.

If the hole is located at the far end of the bag, it may occur that thebag collapses and prevents air from passing via the hole and to thetubes and eventually out. This could imply that a tube-set which has ahole could pass the integrity-test. To avoid this, the bags are ribbedinternally in the longitudinal direction so that there is always aflow-path for the air.

Naturally, an integrity-test according to the present invention cannotreplace the check which the user should always make to the cycler atsuitable occasions. If liquid is present at the bottom of the casing,the reason for this should always be investigated.

A combination of underpressure and overpressure can also possibly beused.

Instead of waiting for a predetermined interval of time, 10 seconds, thepressure can be allowed to drop to a predetermined pressure, for example30 mm Hg, and the time can be measured that it takes to attain thesecond lower pressure.

The order of the two pressure sequences can be reversed so that apossibly greater leakage is detected first by opening the clamparrangements 36 and 37 and thereafter a normal leakage is established.

It is also possible to firstly attain the higher pressure of 40 mm Hgand thereafter allow the pressure to drop with the clamp arrangementsclosed for a certain time, for example 10 seconds, and read the pressureand is thereafter directly open the clamp arrangements and permit thepressure to continue to drop without firstly increasing the pressure andfinally recording the pressure after a further time interval, forexample 9 seconds. The ratio between the pressure differences providesan indication of whether the pressure reduction is quicker when theclamp arrangements are open.

The pressure during the two phases does not need to be the same.Instead, different pressures can be used and the comparison can takeplace on the basis of calculations which are determined theoreticallyand/or empirically.

It is also possible to keep the pressure constant, for example at 40 mmHg, by driving the pump and measuring the quantity of air which is fedinto the chamber which thus will be the same as the leakage.

The above-described methods can be used individually or in suitablecombinations.

The invention has been described above with reference to preferredembodiments of the invention. A skilled person will realise that furtherpossibilities for use of the invention exist which are within the scopeof the invention and such possibilities and modifications are within thescope of the invention. The invention is restricted only by the appendedclaims.

What is claimed is:
 1. A method for testing the integrity of a tube setused in a cycler for peritoneal dialysis comprising a closable housingfor at least a portion of said tube set and pressure means forsubjecting said housing to an underpressure or an overpressure, andincluding clamps for clamping portions of said tube set passing intosaid housing, said tube set containing air and said method comprisingsubjecting said housing to a first overpressure with said clamps closed,whereby a first pressure leakage can be observed, subjecting saidhousing to a second overpressure with said clamps open, whereby a secondpressure leakage can be observed, and comparing said first and secondpressure leakages, whereby action can be taken based upon saidcomparison.
 2. The method of claim 1 wherein said first and secondoverpressures are substantially the same, and wherein said comparing ofsaid first and second pressure leakages determines whether saiddifference or ratio between said first and second pressure leakagesexceeds a predetermined value, whereby action can be taken if saidpredetermined value is exceeded.
 3. The method of claim 1 wherein saidobserving of said first and second pressure leakages comprisesmonitoring said pressure leakage with a pressure sensor, whereby saidpressure leakage comprises a pressure drop over a predetermined timeperiod or until a predetermined pressure drop is obtained within apredetermined time period.
 4. The method of claim 1 wherein saidsubjecting of said housing to said first and second overpressurecomprises connecting an air pump to the lower portion of said housing,and including monitoring the entry of liquid into said air pump.
 5. Themethod of claim 1 including monitoring the presence of liquid in thelower portion of said housing by means of a liquid sensor disposed insaid housing.
 6. Apparatus for testing the integrity of a tube set usedin a cycler for peritoneal dialysis comprising a closable housing for atleast a portion of said tube set, said apparatus comprising: pressuremeans for subjecting said housing to an overpressure or anunderpressure, clamps for clamping portions of said tube set passinginto said housing, whereby when said housing is subjected to a firstoverpressure with said clamps closed a first pressure leakage can beobserved and when said housing is subjected to a second overpressurewith said clamps open a second pressure leakage can be observed, andcontrol means for comparing said first and second pressure leakages,whereby action can be taken based on said comparison.
 7. The apparatusof claim 6 wherein said first and second overpressures are substantiallythe same, and wherein said control means compares said first and secondpressure leakages to determine if the difference or ratio between saidfirst and second pressure leakages exceeds a predetermined value,whereby action can be taken if said predetermined value is exceeded. 8.The apparatus of claim 6 wherein said pressure means comprises apressure sensor for monitoring said pressure leakage, whereby saidpressure leakage comprises a pressure drop over a predetermined timeperiod or until a predetermined pressure drop is obtained within apredetermined time period.
 9. The apparatus of claim 6 wherein saidpressures means comprises an air pump connected to the lower portion ofsaid housing, whereby the entry of liquid into said air pump can bemonitored.
 10. The apparatus of claim 6 including a liquid sensordisposed in said housing for monitoring the presence of liquid in alower portion of said housing.